The case for changing the certification system is overwhelming. Researchers in New York City, North Carolina, Texas and Florida have all shown that teachers with traditional master’s degrees in education are no more effective in the classroom than those who do not have such a degree. Yet a dozen states, including New York, require teachers to get a master’s degree to be fully certified.

School districts in those states and others typically pay teachers 10 percent more if they hold an M. A., and half of all teachers sign up for the pay raise by going through the ed-school-master’s-degree routine. Some teachers, on the verge of retirement, decide to pursue the degree in the last few years of teaching, thereby boosting the pension they will receive. All that money is going for something no one has been able to show has any positive effect on student performance.

Traditional certification requirements also close the school door to minority teachers. In work that I did with Daniel Nadler, we found that the ratio of teachers from African American and Hispanic groups to other adults was higher in states with meaningful alternative certification programs than in states that lack that option. Other studies show that traditional certification programs add nothing to the performance of teachers in classrooms. In other words, certification laws have whitened the teaching force with no apparent benefits to students.

Decades ago, education reformers proposed state certification of teachers in order to take the hiring of teachers out of the hands of local politicians. But the policy has limited the pool of available educators, constrained local school administrators from looking for the best person available, created artificial teacher shortages when economic times are good, and limited minority access to teaching.